BOSPHORUS HAVA YOLLARI TURİZM VE TİCARET ANONİM ŞİRKETİ v. IRELAND JUDGMENT 27 98. Article 177 distinguishes between domestic courts which have a discretion to refer and those courts of last instance for which referral is mandatory. However, according to the CILFIT1 judgment, both categories of court must first determine whether an ECJ ruling on the Community law matter is “necessary to enable it to give judgment”, even if the literal meaning of Article 177 would suggest otherwise: “It follows from the relationship between the second and the third paragraphs of Article 177 that the courts ... referred to in the third paragraph have the same discretion as any other national court ... to ascertain whether a decision on a question of Community law is necessary to enable them to give judgment.” In CILFIT the ECJ indicated that a court of final instance would not be obliged to make a reference to the ECJ if: the question of Community law was not relevant (namely, if the answer to the question of Community law, regardless of what it may be, could in no way affect the outcome of the case); the provision had already been interpreted by the ECJ, even though the questions in issue were not strictly identical; and the correct application of Community law was so obvious as to leave no scope for reasonable doubt, not only to the national court but also to the courts of the other member States and to the ECJ. This matter was to be assessed in the light of the specific characteristics of Community law, the particular difficulties to which its interpretation gave rise and the risk of divergences in judicial decisions within the Community. 99. Once the reference is made, the ECJ will rule on the question put to it and that ruling is binding on the national court. The ECJ has no power to decide the issue before the national court and cannot therefore apply the provision of Community law to the facts of the particular case in question2. The domestic court will decide on the appropriate remedy. IV. OTHER RELEVANT LEGAL PROVISIONS A. The Vienna Convention on the Law of Treaties of 1969 100. Article 31 § 1, entitled “General rule of interpretation”, provides that a treaty shall be interpreted “in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in light of its object and purpose”. Article 31 § 3 further provides that, as well as the context, any subsequent practice in the application of the treaty which establishes the agreement of the parties regarding its interpretation 1. S.r.l. CILFIT and Lanificio di Gavardo S.p.a. v. Ministry of Health, Case 283/81 [1982] ECR 3415. 2. See Jacob Adlerblum v. Caisse nationale d’assurance vieillesse des travailleurs salariés, Case 93-75 [1975] ECR 2147.